Arne and Lian Fogg are fourteen years old twins who live in the pirate town of Fishburn. In reality only Arne is human, while Lian is a Demon of the Well, originating from the miasma of one of the mysterious basins known as the Primordial Wells, scattered around the world . Her true nature is kept secret by her family, not a easy feat with her bad temper for wich her brother had to bacome the responsible one. When the ogress Grezel Rionard humiliates the two Foggs after a brawl at the port, the angry Lian decides to follow her in revenge but ends up setting sail with the orc merchant to Waterose, the Temple City, home to the largest known Primordial Well and the Guardians of The Well, an order specializing in the protection of the miasma and in dealing with the Demons. Arne has to find a way to go to Waterose and find her before the orcs or the Supreme Knight Adam Whitespirit.